#include<fstream>
#include<vector>
using namespace std;
ifstream fin("ciclueuler.in");
ofstream fout("ciclueuler.out");
int n,m,k,x,y;
int v[500001],A[100001],f[500001];
vector < pair<int,int> > L[100001];
int main(){
    fin>>n>>m;
    for(int i=1;i<=m;i++){
        fin>>x>>y;
        L[x].push_back({y,i});
        L[y].push_back({x,i});
        A[x]++;
        A[y]++;
    }
    for(int i=1;i<=n;i++)
        if(A[i]%2==1){
            fout<<-1;
            return 0;
        }
    v[++k]=1;
    while(k){
        if(A[v[k]]==0){
            if(k>1)
                fout<<v[k]<<" ";
            k--;
            continue;
        }
        while(f[L[v[k]].back().second]==1)
            L[v[k]].pop_back();
        int vecin=L[v[k]].back().first;
        f[L[v[k]].back().second]=1;
        A[vecin]--;
        A[v[k]]--;
        L[v[k]].pop_back();
        v[++k]=vecin;
    }
    return 0;
}